Fluid flows are typically turbulent and can be characterized by a wide range of coexisting scales of motion. Increased turbulence in a fluid flow results in an increase in energy dissipation, mixing, heat transfer and drag experienced by an object moving through the fluid. The characterization of turbulence is relevant to air navigation, weather forecasting, climatology, resource management, etc.
A variety of methods have been developed to measure turbulence. For example, Sound Navigation and Ranging (SONAR) techniques can be used to characterize turbulence in the ocean. In another example, Doppler Light Detection and Ranging (LIDAR), interferometers, bistatic radars, etc. can be used to characterize air turbulence. LIDAR is particular suitable for characterizing turbulence because (1) visible light penetrates water well (low absorption, medium scattering); (2) no actual physical contact with the water (around 98% transmission at the air/water interface vs 0.12% for acoustic) thus no perturbation of the flow; and (3) ability to provide range resolved information (i.e., depth profiling).
Turbulence is a critical property of the ocean mixed layer and has a direct impact on ocean heat storage and algae photosynthesis. Observing changes in turbulence at the synoptic scale is quite challenging. Research vessels provide a limited geographic and temporal coverage and most systems used to characterize turbulence use in situ instrumentations which disturbs the flow and affects turbulence itself.